The invention relates to an inclination sensor for measuring angle of inclination with respect to gravity.
Lawn and garden equipment such as tractors and riding lawn mowers are often operated on slopes or grades where there is a risk of roll-over. The operator may be unaware that the equipment is being operated near its roll-over limit. Monitoring the orientation of the equipment and actuating an alarm when the equipment nears the limit may avoid an impending roll-over.
Inclination sensors measure angular orientation and monitor equipment orientation. One conventional type of inclination sensor uses a weight that rolls along a curved surface. Gravity urges the weight to roll to the lowest point along the surface. Light emitters spaced along the surface are located across photo-detectors. The weight blocks the light between emitter-detector pairs as it moves along the surface in response to changing inclination. Determining the location of the weight along the surface enables the inclination angle to be calculated.
This known sensor, however, requires a large number of emitter-detector pairs. The inclination angle is measured in discrete steps and its angular resolution is limited by the spacing of the emitter-detector pairs.
Thus there is a need for an improved inclination sensor. The improved inclination sensor should provide substantially continuous monitoring of inclination angle in its operating range and should not require a large number of detectors.
The invention is an improved inclination sensor. The improved inclination sensor continuously monitors inclination angle with only a single emitter/detector pair, or alternatively, two emitter/detector pairs.
An inclination sensor in accordance with the present invention includes a tubular chamber extending along a curved longitudinal axis. A mass (weight) is located within the chamber, the mass movable along the chamber axis and urged to the lowest point of the chamber by the force of gravity. At least one location sensor is connected to the chamber for determining the location of the mass along the chamber axis. Each location sensor includes a radiation emitter that emits radiation (preferably visible light) from a first position towards the mass for reflecting radiation off the mass and a radiation detector disposed at a second location to detect the radiation reflected from the mass. The radiation detector generates a signal representing the intensity of the reflected light at the detector and thus the distance of the mass along the axis from the second position. The inclination of the inclination sensor is calculated from the signal.
In a preferred embodiment the inclination sensor includes a pair of location sensors, the sensors located at opposite ends of the chamber. A liquid is sealed in the chamber and attenuates the light traveling through the chamber. The liquid includes a coloring agent that couples the path of the light transmission along the chamber axis and enables the light to follow the curvature of the chamber.